International Appliance Manufacturing 2008 - (Page 23) Extending Efficiency Advanced control methods more accessible to wider range of appliances. Jorge Zambada, is senior applications engineer, Digital Signal Controller Div., Microchip Technology, Chandler, Ariz. Advanced motor-control techniques are a practical necessity because they enable more efficient and quieter appliances. In the past, these advanced control techniques were only available as proprietary solutions, and hence were limited in scope to a few high-end appliances. Given the drive toward efficient appliances running on “green” power, which is mandated by regulations and customer preferences, these motor-control algorithms are now being sought by designers of all classes of appliances. Thanks to the new generation of digital-signal-controllers (DSCs), the cost-effective implementation of advanced motor-control algorithms has become a reality. From the slew of advanced motor-control techniques available today, the Field-Oriented Control (FOC) algorithm has solid claims on being the leading technique for helping to save energy and building quieter appliances. DSC-based FOC control over a Permanent-Magnet Synchronous Motor (PMSM) will serve as an example. Sensor-less FOC control has advantages over the sensor-based version, because it overcomes impediments in some applications that cannot afford to deploy position or speed sensors. In certain compressor applications, for example, the motor is flooded in oil, making wire-harness placements difficult. Today’s motor-control solutions rely on costly custom ASICs to implement a FOC algorithm. Further compounding the difficulty is the fact that these ASIC-based FOC algorithms and related A Microchip dsPIC digital signal controller. libraries are inflexible — users cannot tailor the FOC algorithm based on the application requirements. Additionally, delivering green power to the appliance requires the addition of a Power Factor Correction (PFC) circuit. Existing appliance power stages are also dependent on costly custom ASICs to implement the PFC block. Versatile DSCs are suitable for implementing advanced motor- International Appliance Manufacturing 2008 23
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